The invention relates generally to an electric device with rotor and stator and particularly to an electrical device including a sealing assembly protecting the stator from corrosive environments.
Industrial electric devices, such as motors, often include a stationary portion, or stator, and a rotating portion, or rotor. Typically, the rotor and the stator are configured to produce opposing magnetic fields, thereby generating rotational motion in the rotor that is used to perform mechanical work. In the oil and gas industry, the rotor and stator assemblies can operate in a process gas, which can also serve as a cooling agent. The process gas typically is natural gas at pressures of about 10 bar to about 200 bar. Unfortunately, natural gas can have a high degree of contaminants. These contaminants can include corrosive agents such as hydrogen sulfide (H2S), water, CO2, oil, and others. In particularly aggressive conditions, the combination of water and H2S leads to more corrosive gases such as what is called wet sour gas or at higher concentrations, acid gas. The presence of a process gas environment that contains the above contaminants poses a significant risk to the vulnerable components of the stator assembly.
Typically a gap separates the stator assembly from the rotor assembly. In order to maximize the magnetic field strength between the stator and rotor assembly, this gap is made as small as possible while still meeting mechanical clearance requirements between the rotor shaft and the stator. Current stators are either encapsulated or non-encapsulated. In the case of encapsulated stators, the stator encapsulation protects the stator components from the process environment of the rotor assembly.
The stator encapsulators generally need to withstand the large pressure differentials, large temperature gradients, and mechanical vibrations during operation. In harsh operating environments, the sections of the encapsulator located in the gap between the stator and the rotor shaft should minimize leakage of corrosive process gases, should resist corrosion in the harsh process gas environment, should be readily joinable to other sections of the encapsulator, and should minimize eddy current losses to reduce overall electrical losses in the machine.
Therefore, there is a need for providing a compatible, low loss material and processes for assembling the same for stator encapsulation.